Correlation of Plant Condensed Tannin and Nitrogen Concentrations to White-Tailed Deer Browse Preferences in the Cross Timbers

Abstract

Chemical plant defenses such as condensed tannins (CT) have the potential to reduce insect herbivory.  Condensed tannins sometimes also reduce ruminant herbivory as a result of decreased palatability and nutrient availability in gastro-intestinal systems.  However, when consumed as 1-3% of diets, CT can be beneficial to ruminants as anthelminthics and by binding to plant proteins to enhance rumen-bypass protein.  Given that plant nitrogen and CT are important ruminant nutritional factors, this study was designed to investigate correlations between deer browse preference and crude protein (CP) and/or CT concentration.  In this study we collected 56 preferred warm-season white-tailed deer browse species within the cross-timbers region of Texas and analyzed for CT and CP concentrations.  Plant CT varied from 78.4% to 0.5% (dry matter basis, Schinopsis balansae CT standard) and CP ranged from 23.8% to 5.0%.  However, there was no correlation between plant CT or CP concentrations and published deer preference.  Our study suggests that, while CT and CP may be important components of the white-tailed deer diet, preference is not based solely on CT or CP concentrations.  Further research is needed to determine if plant maturity or surrounding vegetation confound correlations between white-tailed deer feed preferences and CT or CP in those selectively browsed plants. Use of a self-standard from each plant species to measure CT of that species may also change correlations.